Minimization Drive Test (MDT) is used for reducing drive test efforts by retrieving measurement and positioning information from active user equipments in a wireless network. MDT benefits the network operators to reduce operational cost involved in frequent drive tests.
Typically, a base station configures UEs for MDT campaign based on a configuration shared by a MDT server. Accordingly, each UE performs the MDT in both radio resource connection (RRC) idle and connected modes and the UE periodically logs the MDT data in the IDLE mode based on the MDT configuration received while in RRC Connected mode. The MDT log data includes radio condition measurement information perceived by the UE along with available location and time information associated with the radio measurements. The location information available with the UE can be Global Navigation Satellite System information or radio frequency fringerprint information of neighbouring cells.
As an example, in third generation partnership project (3GPP) long term evolution (LTE), in RRC connected mode, the UE instantaneously reports the MDT log data to the base station. Whereas in idle mode, the UE logs the MDT data with periodicity in terms of their DRX cycles as specified in the received MDT configuration. Ideally, a UE configured for MDT logging shall indicate presence of MDT log data to the base station during transitions to the connected mode. The base station then retrieves the MDT log data buffered by the UE during the idle mode using RRC signalling, i.e., in LTE using information transfer procedure UE transfers the MDT log data to the base station and henceforth to the MDT server for network optimizations.
UE information is a request response procedure in which uplink response message uses the same transaction ID as indicated in DL request message. The UE is thereby allowed to transfer the MDT log data equal to a size of packet data convergence protocol (PDCP) service data unit (SDU) in a UL response message. The size of the PDCP SDU in LTE for transfer of a single RRC message is 8188 bytes.